This is an inbuilt function function provided by PPWIZARD.
This routine takes a single parameter which is the include level that you are interested in. The full name of the input file at that level is returned.
If you don't pass any value then the current level is assumed. If you pass an invalid value the empty string ("") is returned.
This rexx routine does a similar job to the "<?InputComponent>" special variable (but for any level - not just the current one).
Simple example in which one file works out who included it and at what line:
;--- Work out who included this file (and what line) --- #evaluate ParentFile ^InputComponentLevel(<?IncludeLevel>-1)^ #if '<$ParentFile>' = '' <P>There is no parent file! #elseif #evaluate ParentLine ^InputComponentLineLevel(<?IncludeLevel>-1)^ <P>The parent file is: "<$ParentFile>" (line <$ParentLine>) #endif